A187108 Odd numbers not in the trajectory of a smaller number under the Collatz (3x+1) iteration.

1, 3, 7, 9, 15, 19, 21, 25, 27, 33, 37, 39, 43, 45, 51, 55, 57, 63, 69, 73, 75, 79, 81, 87, 93, 97, 99, 105, 109, 111, 115, 117, 123, 127, 129, 133, 135, 141, 145, 147, 151, 153, 159, 163, 165, 169, 171, 177, 181, 183, 187, 189, 195, 199, 201, 207, 213, 217

Offset: 1

Author

Jimin Park, Mar 05 2011

Keywords

• nonn

Comments

These are the odd numbers in A061641, which gives a more detailed explanation. - T. D. Noe, Mar 05 2011

Crossrefs

Cf. A061641.

Programs

ActionScript

// AS3
var a:Array=new Array();
var i:int;
var n:int=0;
var ni:int;
var s:String='';
for (i=0;i<50;i++){
while(a[n]!=undefined) n++;
s+=String(2*n+1)+',';
a[n]=1;
ni=2*n+1;
while(ni>=2*n+1&&ni>1){
ni=3*ni+1;
while(ni%2==0)ni/=2;
a[(ni-1)/2]=1;
}
}
trace(s);